The present disclosure relates to a semiconductor integrated circuit, an information processing device and an image forming apparatus and particularly to a technique to address unnecessary radiation.
Electromagnetic interference (EMI) is a phenomenon in which a trouble (e.g. malfunction) occurs in an electronic device due to electromagnetic waves radiated from the device called unnecessary radiation. A level of unnecessary radiation is determined by standards such as IEC (international Electrotechnical Commission) standards and CISPR (Comité International Spécial des Perturbations Radioélectriques) standards.
The following technique has been proposed as a technique to address unnecessary radiation. In a semiconductor integrated circuit with a plurality of circuit blocks and delay elements provided in a plurality of stages through which clocks for operating these circuit blocks are passed, timings of clocks to be supplied to a plurality of circuit blocks are made different from each other by making the number of the delay elements, through which the clock passes, different depending on the circuit block.
The above conventional technique uses the delay elements and has the following problem. In the delay element, a delay time cannot have a fixed value due to variations in the operating temperature of the semiconductor integrated circuit and semiconductor processes at the time of manufacturing the semiconductor integrated circuit. Thus, a level of unnecessary radiation differs in each semiconductor integrated circuit. Some of semiconductor integrated circuits have a level of unnecessary radiation exceeding a standard value. Further, in the case of making timings of clocks to be supplied to a plurality of circuit blocks largely different, delay elements provided in a multitude of stages are necessary. Thus, a circuit size becomes larger.
The above conventional technique is a technique for suppressing a level of unnecessary radiation in one semiconductor integrated circuit (one IC chip) and does not consider the suppression of the level of unnecessary radiation in all semiconductor integrated circuits if an information processing device includes a plurality of semiconductor integrated circuits (a plurality of IC chips).
The present disclosure aims to provide a semiconductor integrated circuit, an information processing device and an image forming apparatus capable of suppressing a level of unnecessary radiation in all of a plurality of semiconductor integrated circuits.